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Synthesis of pyrroles
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A highly efficient Cu-catalyzed tandem C-N bond-forming reaction of
1,4-dihalo-1,3-dienes allows the synthesis of pyrroles and heteroarylpyrroles
with a wide variety of functional groups and substitution patterns from readily
available precursors.
R. Martín, C. H. Larsen, A. Cuenca, S. L. Buchwald, Org. Lett., 2007,
9, 3379-3382.
An efficient copper-catalyzed double alkenylation of amides with (1Z,3Z)-1,4-diiodo-1,3-dienes
affords di- or trisubstituted N-acylpyrroles in good yields using CuI as
the catalyst, Cs2CO3 as the base, and rac-trans-N,N'-dimethylcyclohexane-1,2-diamine
as the ligand.
X. Yuan, X. Xu, X. Zhou, J. Yuan, L. Mai, Y. Li, J. Org. Chem., 2007,
72, 1510-1513.
A range of 2,5-disubstituted and 2,4,5-trisubstituted pyrroles can be
synthesized from dienyl azides at room temperature using ZnI2 or Rh2(O2CC3F7)4
as catalysts.
H. Dong, M. Shen, J. E. Redford, B. J. Stokes, A. L. Pumphrey, T. G. Driver, Org. Lett., 2007,
9, 5191-5194.
An efficient, solvent-free, microwave-assisted coupling of
chloroenones and amines on the surface of silica gel gave 1,2-disubstituted
homochiral pyrroles in good yields.
F. Aydogan, A. S. Demir, Tetrahedron, 2005,
61, 3019-3023.
The CuI/N,N-dimethylglycine-catalyzed reaction of amines with
γ-bromo-substituted γ,δ-unsaturated ketones in the presence of K3PO4
and NH4OAc gave the corresponding polysubstituted pyrroles in very
good yields.
Y. Pan, H. Lu, Y. Fang, X. Fang, L. Chen, J. Qian, J. Wang, C. Li, Synthesis, 2007,
1242-1246.
A mild, gold(I)-catalyzed acetylenic Schmidt
reaction of homopropargyl azides gave regiospecific substituted pyrroles. A mechanism in which azides serve as nucleophiles toward gold(I)-activated alkynes
with subsequent gold(I)-aided expulsion of dinitrogen is proposed.
D. J. Gorin, N. R. Davis, F. D. Toste, J. Am. Chem. Soc.,
2005, 127, 11260-11261.
Various 2-alkyl-5-aryl-(1H)-pyrrole-4-ol derivatives were synthesized via
a multicomponent reaction of β-dicarbonyl compounds with arylglyoxals in the
presence of ammonium acetate in water at room temperature.
B. Khalili, P. Jajarmi, B. Eftekhari-Sis, M. M. Hashemi, J. Org. Chem., 2008,
73, 2090-2095.
An efficient and regioselective palladium-catalyzed cyclization of internal
alkynes and 2-amino-3-iodoacrylates gave good yields of highly
functionalized pyrroles.
M. L. Crawley, I. Goljer, D. J. Jenkins, J. F. Mehlmann, L. Nogle, R.
Dooley, P. E. Mahaney, Org. Lett., 2006, 8, 5837-5840.
Two methods for the regioselective synthesis of tetra- and trisubstituted N-H
pyrroles from starting vinyl azides have been developed: A thermal pyrrole
formation via the 1,2-addition of 1,3-dicarbonyl compounds to 2H-azirine
intermediates generated in situ from vinyl azides and a Cu(II)-catalyzed
synthesis with ethyl acetoacetate through a 1,4-addition.
S. Chiba, Y.-F. Wang, G. Lapointe, K. Narasaka, Org. Lett., 2008,
10, 313-316.
S. Chiba, Y.-F. Wang, G. Lapointe, K. Narasaka, Org. Lett., 2008,
10, 313-316.
The reaction of an enaminone, which can be derived from two primary amines and
diketene, in the presence of nitrostyrene gives functionalized pyrrole
derivatives in very good yields.
A. Alizadeh, A. Rezvanian, H. R. Bijanzadeh, Synthesis, 2008,
725-728.
A silver(I)-promoted oxidative
cyclization of homopropargylamines at room temperature provides pyrroles.
Homopropargylamines are readily available by the addition of a propargyl
Grignard reagent to Schiff bases.
S. Aggarwal, H.-J. Knölker, Org. Biomol. Chem., 2004, 2,
3060-3062.
A general, highly flexible Cu-catalyzed domino C-N coupling/hydroamination
reaction constitutes a straightforward alternative to existing methodology
for the preparation of pyrroles and pyrazoles.
R. Martin, M. R. Rivero, S. L. Buchwald, Angew. Chem. Int. Ed., 2006, 45, 7079-7082.
An efficient and highly versatile microwave-assisted Paal-Knorr condensation
of various 1,4-diketones gave furans, pyrroles and thiophenes in good yields.
In addition, transformations of the methoxycarbonyl moiety, such as Curtius
rearrangement, hydrolysis to carboxylic acid, or the conversion into amine
by reaction with a primary amine in the presence of Me3Al, are
described.
G. Minetto, L. F. Raveglia, A. Sega, M. Taddei, Eur. J. Org. Chem., 2005,
5277-5288.
A direct synthesis of pyrroles from imines, acid chlorides, and alkynes
mediated by isocyanides proceeds with a range of substrates, providing a method
to generate various pyrroles in high yield. Mechanistic studies suggest a
generation of imino analogues of münchnones, which can undergo in situ coupling
with alkynes to liberate isocyanate and form the pyrrole product.
D. J. St. Cyr, N. Martin, B. A. Arndtsen, Org. Lett., 2007,
9, 449-452.
The nucleophilic addition of sodium azide to 1,2-allenyl esters regio- and
stereoselectively generates
vinyl azides in excellent yields.
A sequential reaction for the synthesis of pyrroles using 1-allyllic 1,2-allenyl
esters as substrates is developed
on the basis of a domino process involving nucleophilic addition,
cycloaddition, denitrogenation, and aromatization.
X. Huang, R. Shen, T. Zhang, J. Org. Chem., 2007,
72, 1534-1537.
The synthesis of N-acylpyrroles from primary aromatic amides and
excess 2,5-dimethoxytetrahydrofuran in presence of one equivalent of thionyl
chloride offers short reaction times, mild reaction conditions, and easy
workup.
A. R. Ekkati, D. K. Bates, Synthesis, 2003, 1959-1961.
Propargyl vinyl ethers and aromatic amines are effectively converted into tetra- and pentasubstituted
5-methylpyrroles through a
silver(I)-catalyzed propargyl-Claisen rearrangement, an amine condensation, and
a gold(I)-catalyzed 5-exo-dig heterocyclization in a convenient one-pot process.
J. T. Binder, S. F. Kirsch, Org. Lett.,
2006, 8, 2151-2153.
Various 2,3,4-trisubstituted pyrroles are easily accessible in one step from
readily available acetylenes and acceptor-substituted methyl isocyanides by base-mediated
or copper-catalyzed cycloadditions. Scope and limitations of both pyrrole
syntheses are discussed.
O. V. Larionov, A. de Meijere, Angew. Chem. Int. Ed., 2005,
44, 5664-5667.
A New Use of Wittig-Type Reagents as 1,3-Dipolar Cycloaddition Precursors
and in Pyrrole Synthesis
D. J. St. Cyr, B. A. Arndtsen, J. Am. Chem. Soc.,
2007,
129, 12366-12367.
A
novel and efficient multicomponent reaction of N-tosylimines, DMAD,
and isocyanides for the synthesis of 2-aminopyrrole systems was uncovered.
V. Nair, A. U. Vinod, C. Rajesh, J. Org. Chem., 2001, 66,
4427-4429.
A new microwave-assisted rearrangement of 1,3-oxazolidines scaffolds is the
basis for a new, metal-free, direct, and modular construction of
tetrasubstituted pyrroles from terminal-conjugated alkynes, aldehydes, and
primary amines under very simple and environmental-friendly experimental
conditions.
D. Tejedor, D. González-Cruz, F. García-Tellado, J. J. Marrero-Tellado, M.
L. Rodríguez, J. Am. Chem. Soc.,
2004, 126, 8390-8391.
Coupling of acetylene, nitrile, and a titanium reagent generated new
azatitanacyclopentadienes in a highly regioselective manner. The subsequent
reaction with sulfonylacetylene and electrophiles gave substituted pyridines
virtually as a single isomer. Alternatively, the reaction of
azatitanacyclopentadienes with an aldehyde or another nitrile gave furans or
pyrroles having four different substituents again in a regioselective manner.
D. Suzuki, Y. Nobe, R. Tanaka, Y. Takayama, F. Sato, H. Urabe, J. Am. Chem. Soc.,
2005, 127, 7474-7479.
An efficient synthesis of 2,3,4-trisubstituted pyrroles via intermolecular
cyclization of alkylidenecyclopropyl ketones with amines was observed. A
mechanism involving a distal cleavage of the C-C bond of the cyclopropane ring
is discussed.
L. Lu, G. Chen, S. Ma, Org. Lett.,
2006, 8, 835-838.
Several aryl-substituted pyrrole derivates were prepared conveniently in a
microwave-assisted one pot-reaction from but-2-ene-1,4-diones and
but-2-yne-1,4-diones via Pd/C-catalyzed hydrogenation of the carbon-carbon
double bond/triple bond followed by amination-cyclization.
H. S. P. Rao, S. Jothilingam, H. W. Scheeren, Tetrahedron, 2004, 60, 1625-1630.
1,3,4-triaryl-2,5-dihydropyrroles were synthesized using the McMurry coupling
reaction as key step. A facile and reliable non-catalytic photoconversion of
1,3,4-triaryl-2,5-dihydropyrroles furnished 1,3,4-triarylpyrroles in good yields.
D. X. Zeng, Y. Chen, Synlett,
2006, 490-492.
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